Prakt. Met. Sonderband 50 (2016) 13 
Best of Schadensanalyse an Turbomaschinen — die Highlights aus 20 
Jahren Laborpraxis 
Best of Failure Analysis of Turbomachinery Components — Highlights 
From Two Decades’ of Laboratory Practice 
A. Neidel, E. Cagliyan, B. Fischer, T. Gidicke, M. Giller, V. Hartanto, C. Kramm, S. Riesenbeck, 
T. Ullrich, S. Wallich" 
D Siemens AG. Power and Gas Division, Gas Turbines and Generators, Gasturbinenwerk Berlin 
Tum 
Abstract 
In this contribution, the most interesting and educating failure cases are presented that the author 
came across during his some twenty years of laboratory practice as manager of the Materials 
Testing Laboratory of the Berlin Gas Turbine Plant of Siemens’ Power and Gas Division. The case 
studies are presented and categorised in accordance with VDI Guideline 3822, the German failure 
analyst’s guide to the subject of how to organise and run a root cause failure analysis. An effort was 
made to have each of the main four categories of failure causes represented, namely failures due to 
mechanical loading, corrosive failures, failures due to thermal loading, and tribological failures. 
Case studies include turbomachinery components that failed due to tensile overload, stress 
corrosion cracking, intergranular corrosion, hydrogen embrittlement, hot cracking, fretting, erosion, 
and galling. Affected components include valves, retaining rings, tubing and piping, burners, rotor 
disks, lifting lugs, and casings. Some of the presented cases were published in the new section 
BY vives. “Failure Analysis” of Practical Metallography between October 2011 and the present time. Others 
20 um : . . 
- were oral presentations at the Metallography conferences and at the annual failure analysis 
he Vergrößerung. conferences “VDI Jahrestagung Schadensanalyse”, held during that time. The focus of discussion of 
the failure cases in this paper is the metallurgical evaluation of failure causes. This is the approach 
taken in many small and industrial laboratories. A holistic approach of a failure case, which 
includes calculation and simulation methods such as finite element analysis, and which also implies 
a knowledge of the service stresses intended by design as well as the actual loading situation of the 
failed part, is not the aim of this contribution. 
1 Mechanical Failures — High Cycle Fatigue Fracture of a Dampening Pin 
Dampening pins are used to prevent airfoils of large moving blades of the last stages of the turbine 
sections of gas turbines from vibrating. This design principle has also been used in steam turbines 
for many years. In most cases, the pins are fastened to the bore of one airfoil by means of a flat pin 
head and a shrunk sleeve on the other side of the airfoil and are only loosely attached to the adjacent 
airfoil by the loose end of the pin that also sits in a bore. In modern machines, dampening pins are 
not employed any more because of aerodynamic reasons, except for variable speed turbines.